What Is WVTR (Water Vapor Transmission Rate)?
Direct Answer
WVTR measures how much water vapor passes through a diaper backsheet per unit area and time, quantifying true breathability.
Key Takeaways
- WVTR measures how much water vapor passes through a diaper backsheet per unit area and time, quantifying true breathability.
- How it works: WVTR is tested by sealing a film over a water cup and measuring weight loss over time (g/m2/day).
- Breathable diaper films typically show WVTR of thousands of g/m2/day
- Myth: Air permeability equals WVTR. They measure different things — WVTR is specifically vapor passage
How WVTR (Water Vapor Transmission Rate) Works
WVTR is tested by sealing a film over a water cup and measuring weight loss over time (g/m2/day). Higher WVTR means more vapor escapes, reducing internal humidity. Micro-porous films achieve high WVTR while blocking liquid. It is the objective metric behind 'breathable' claims.
Examples and Applications
- Breathable diaper films typically show WVTR of thousands of g/m2/day
- WVTR testing distinguishes real breathability from marketing
WVTR (Water Vapor Transmission Rate) vs. Related Terms
| Term | What it is | Key difference |
|---|---|---|
| Air permeability | WVTR (Water Vapor Transmission Rate) | Air permeability measures air flow; WVTR measures water vapor passage specifically |
Limitations and Common Misconceptions
- Myth: Air permeability equals WVTR. They measure different things — WVTR is specifically vapor passage
- Myth: Higher WVTR always means better. It must balance with leak protection and strength
What does WVTR measure?
Water vapor passing through a film per area and time (g/m2/day) — the objective breathability metric.
Why is WVTR important?
High WVTR releases moisture vapor, reducing heat and wetness in the diaper.
References
- Pampers Official - What's in a Pampers diaper (component materials) — 品牌官方 (accessed 2026-08-02)
- JP CIA (industry) - Baby diaper material: key components and their functions — 行业媒体 (accessed 2026-08-02)